The vertical permeability of formation is a very important physical parameter in the field of petroleum exploration and development, and a formation tester is often used to obtain the parameter.
At present, a representative formation tester MDT (Modular Formation Dynamics Tester) usually uses a three-probe combination module and related equipment thereof to obtain the vertical permeability of formation. As shown in FIG. 1, after the instrument is lowered into the target layer, the three probes are deployed to complete setting, and a channel is set up between the formation and the instrument. The testing process is as follows: shutting 3# probe, opening 1# and 2# probes, using a pump to extract formation fluid by 1# probe, detecting the change of pressure at the 2# probe, and establishing the relationship between the change of pressure and the distance between 1# and 2# probes as well as the suction amount, thereby obtaining the vertical permeability of formation. The premise of this testing method is that the fluid must satisfy spherical percolation theory. However, the downhole fluid is more often columnar flow and due to various interference factors, the precision of vertical permeability of formation obtained by this manner is limited, even is not in an order of magnitude. In the formation testing instrument, in order to obtain the vertical permeability of formation and the premise of use thereof is that the fluid must satisfy spherical percolation theory. However, due to various interference factors of this testing method, the precision of vertical permeability is limited.
In addition, for some complex formation such as low porosity and low permeability, the conventional method of obtaining fluid sample of complex formation such as low permeability by using formation tester is using a dual packer module and the two rubber sleeves thereof. After the instrument reaches the target layer, the two rubber sleeves of the dual packer are deployed by hydraulic pressure so as to set a section of formation, then using pump to suck and sample. Conventional probe uses Packer rubber to set one point, while the dual packer sets a segment of space and thus the suction area thereof is large so as to avoid influence of low permeability. But the main drawbacks of this method are as follows: the amount of contaminated fluid is large due to the large setting range; in order to obtain the real formation fluid, it usually needs quite a long time (from a dozen hours to dozens of hours, sometimes even up to half a month) to exclude the contaminated fluid, which greatly increases the operation cost (the offshore operation costs around 1 million RMB per day); meanwhile, the instrument being placed under the downhole for long time will greatly increase the cost and risk of downhole operation. Therefore, there are problems such as many interference factors as well as low testing precision, etc, in the existing formation testing instrument technology.